A well-known SMT technology is used for mounting a semiconductor package with a plurality of outer terminals on a printed circuit board (PCB). Because of the outer terminals of the semiconductor package become more and more, the pitch of the outer terminals also becomes smaller and smaller. Conventionally all the outer terminals have to mount on the corresponding contact pads of the PCB via solder paste. A plurality of pre-solders are formed on the contact pads prior to SMT processes. When the outer terminals of the semiconductor package are pressed on the pre-solders, the flowing direction of the pre-solders becomes uncontrollable which may easily spread out and cause bridging between two adjacent contact pads.
A method of surface mounting semiconductor package is disclosed in R.O.C. Taiwan Patent No. 483299. A semiconductor package has an exposed die pad. A solder receiving groove is formed on the outside surface of the die pad. A first solder is formed on a ground panel of a printed circuit board (PCB). A plurality of second solders are formed on a plurality of fingers of the PCB. During the reflowing process, the first solder connects the ground panel and die pad, the second solders connect the fingers and the outer leads of the semiconductor package. The solder receiving groove can receive the first solder to avoid solder beads formation and contamination to the outer leads or fingers. However, bridging problems of the second solders between the fingers cannot be solved by means of the solder receiving groove.